This invention relates to melt adhesive compositions especially useful in adhering polyolefin bodies to themselves, to other polyolefin bodies and to other non-polyolefinic bodies comprising a blend of (1) an amorphous polypropylene (amorphous polyalphaolefins), (2) a selectively hydrogenated monoalkenyl arene/conjugated diene block copolymer of linear or radial configuration and (3) a tackifier. 2. Description of the Prior Art
The preparation of adhesives containing amorphous polypropylene and block copolymers containing unsaturated mid block copolymers, for example, polystyrene-polybutadiene-polystyrene (S-B-S) or polystyrene-polyisoprene-polystyrene (S-I-S), tackifier and a rubber-extending oil is known, as evidenced, for example, in U.S. Pat. No. 3,862,068 to Russell. Such adhesives have limited elevated temperature melt stability, limited resistance to O.sub.2 and UV, but, most important, exhibit limited performance characteristics on untreated polyolefin surfaces wherein high bond integrity and durability are also required. U.S. Pat. No. 3,686,107 to Russsell also discloses similar compositions having similarly undesired characteristics noted above. St. Clair et al in U.S. Pat. No. 4,296,008 prepares a sealant composition containing a selectively hydrogenated S-B-S and S-I-S block copolymer in combination with tackifying resins, plasticizers and solvents. U.S. Pat. No. 4,138,378 to Doss also discloses a sealant formulation containing selectively hydrogenated block copolymers, a polyalkene plasticizer, a tackifying resin and a filler. St. Clair et al in U.S. Pat. No. 4,286,077 disclose the use of selectively hydrogenated block copolymers in combination with a tackifier and a plasticizer to obtain a pressure sensitive adhesive. Additional variants in adhesive preparations involving the use of hydrogenated block copolymers are described in U.S. Pat. No. 4,151,057 to St. Clair et al.
The patents discussed above are exemplary of the prior art involving the utilization of various types of block copolymers in the preparation of adhesives and sealants. Obviously, none of these references discloses the use of an amorphous polypropylene in combination with selectively hydrogenated monoalkenyl arene/conjugated diene block copolymers and tackifiers. We have discovered that such combinations containing an amorphous polypropylene exhibit excellent adhesivity to untreated polyolefins and are useful in various plastic fabrication and assemblies involving such surfaces.